As childhoods go, Gil Rossellini's sounds idyllic. As he sits in the courtyard of a villa in Venice, the dapper Italo-Indian producer reminisces about long, lazy family holidays spent with his extended family. He was very close to his father. Both shared a passion for racing cars and machinery. At home, they built a special lab where they fooled around with lenses, movie cameras and Moviolas. "There was this 60-year-old man and this 10-year-old boy, always tinkering together," he says, evoking an image of a sorcerer and his apprentice.

In theory, Rossellini is giving me an interview to promote The Princess of Mount Ledang, the first Malaysian film ever to screen at an international film festival. He co-produced this 15th-century romantic epic, which is set at the time of the Melaka sultanate. Later in the day, he is due to meet Malaysia's crown prince and its minister of tourism, who are coming to the Lido to support the premiere. Rossellini proselytises on behalf of the movie, trumpeting its importance to Malaysian culture and to the local film industry in particular. Somehow, though, our conversation keeps twisting back to his family.

Gil was the adopted son of Roberto Rossellini, one of the most influential directors in cinema history. His mother, Indian writer Sonali Das Gupta, married Rossellini when they eloped in the late 1950s, after the Italian director's relationship with Ingrid Bergman had broken down.

One might think Rossellini's rift with Bergman would have split the family, but Gil insists this was never the case. "Ours was a very patriarchal and tribal family. We all grew up together. The previous wives were friends with one another. When my mother arrived from India, she had a call from the first wife, who warned her, 'Be careful with that man.'"

In the summer, the entire Rossellini clan would decamp to a house by the sea - seven kids from three different marriages, various nannies and several of the kids' friends. Two of the wives would stay the whole time. There would be fleeting visits from Ingrid Bergman, film and theatre commitments permitting. Rossellini himself would turn up at weekends in his grand Ferrari.

Gil was aware that his father was a film-maker, but didn't know much about his work. When he was 12, he worked as a runner on one of his father's films, Acts of the Apostles. "It was heaven on earth because it was shot in Tunisia in the middle of the school year," he says. "But when I was older, 16 or 17, I considered having to be on the set with my father as child abuse. It wasn't really fun."

At home, though there was a constant stream of visitors from the movie world (Charlie Chaplin and Vittorio de Sica among them), no one talked much about cinema. When Gil started going to films himself, he'd see "things like M*A*S*H or Easy Rider - films of my generation". It was only two years after his father's death, when Gil and his sister Isabella were invited to a retrospective of his father's films in Charleston, South Carolina in 1979, that he realised that there was more to the old man's work than he had imagined. "I saw all his films in a space of two weeks. And I thought, 'Oh, shit! He was a really great film-maker.'"

Gil's favourite of his father's films is the neo-realist classic Germany Year Zero. "That is not to do with the film itself - it has more to do with the man. Consider - my father was an Italian, part of the resistance movement. He had been prosecuted on so many fronts by the Nazis. He had been captured and had to escape - otherwise he would have been killed himself. One year after the end of the war, he goes to Berlin to make a film about the drama of the German people. To me, somebody who has the courage and clarity of mind to set aside all feelings of personal hatred - that is an example I have always wanted to follow."

At college in the US, Gil studied physics and mathematics. "That was his dream. I was good at maths at school and, like most fathers, he had a dream of me doing what he would have liked to do." Gil's obsession, though, was music. He wasn't especially successful in his chosen career. At one stage in the early 1980s, he found himself living penniless in New York. His then brother-in-law Martin Scorsese (married to his sister Isabella) offered him a job as a production assistant on The King of Comedy in 1983. The following year, he worked with Sergio Leone on Once Upon a Time in America, and his own career in the movies began in earnest.

Gil now has his own production and distribution company, Rossellini and Associates. He has produced and directed many documentaries. (The latest, A Hole in the Wall, about slum children in India learning to use computers and the internet, will screen in London later this year.) Inevitably, his own achievements pale in comparison with those of his father. "But it's not a shadow - my father casts a bright light of protection and of pride and joy."

In a break from his duties promoting The Princess of Mount Ledang, Gil is planning to attend the launch of yet another biography of Roberto Rossellini. He doesn't have much faith that it will capture the personality of the man he remembers.

"Each of the biographies I have read has some elements which are real and some which are fantasy. It's not the fault of the writers. It's just that my father and most of his friends were the greatest liars on earth. They would make up stories about what they did 20 years, five years ago or even last night. They were great storytellers. That was why my father was a great film-maker. He could tell the story of lighting up a cigarette and turn it into the invention of fire."